Refactor warnings and errors (#1728)

* Remove `err` and `warn`, keep `errx` and `warnx`, using them in RGBGFX too

* Separate RGBGFX and RGBLINK warnings/errors from main options

* Separate `report` function into `error` and `fatal` messages

* Implicit newlines for most RGBASM errors

src/asm/main.cpp

@@ -3,8 +3,10 @@
 #include "asm/main.hpp"
 
 #include <algorithm>
+#include <errno.h>
 #include <limits.h>
 #include <memory>
+#include <stdarg.h>
 #include <stdlib.h>
 #include <string.h>
 #include <time.h>
@@ -109,6 +111,19 @@ static void printUsage() {
 }
 // LCOV_EXCL_STOP
 
+[[gnu::format(printf, 1, 2), noreturn]]
+static void fatalWithUsage(char const *fmt, ...) {
+	va_list ap;
+	fputs("FATAL: ", stderr);
+	va_start(ap, fmt);
+	vfprintf(stderr, fmt, ap);
+	va_end(ap);
+	putc('\n', stderr);
+
+	printUsage();
+	exit(1);
+}
+
 int main(int argc, char *argv[]) {
 	time_t now = time(nullptr);
 	// Support SOURCE_DATE_EPOCH for reproducible builds
@@ -198,7 +213,9 @@ int main(int argc, char *argv[]) {
 				dependFileName = "<stdout>";
 			}
 			if (dependFile == nullptr) {
-				err("Failed to open dependfile \"%s\"", dependFileName); // LCOV_EXCL_LINE
+				// LCOV_EXCL_START
+				errx("Failed to open dependfile \"%s\": %s", dependFileName, strerror(errno));
+				// LCOV_EXCL_STOP
 			}
 			break;
 
@@ -386,15 +403,9 @@ int main(int argc, char *argv[]) {
 	}
 
 	if (argc == musl_optind) {
-		fputs(
-		    "FATAL: Please specify an input file (pass `-` to read from standard input)\n", stderr
-		);
-		printUsage();
-		exit(1);
+		fatalWithUsage("Please specify an input file (pass `-` to read from standard input)");
 	} else if (argc != musl_optind + 1) {
-		fputs("FATAL: More than one input file specified\n", stderr);
-		printUsage();
-		exit(1);
+		fatalWithUsage("More than one input file specified");
 	}
 
 	std::string mainFileName = argv[musl_optind];